Method and device for measuring electromagnetic waves emanating from a melt

ABSTRACT

In a method for determining electromagnetic waves originating from the interior of a melt ( 3 ), in particular a metal melt, a gas-filled hollow space ( 26 ) is formed within the melt ( 3 ) by blowing in gas and electromagnetic waves emitting from the melt ( 3 ) are observed through the blown-in gas and evaluated by feeding the electromagnetic waves via an optical system ( 20 ) to a detector ( 22 ) for determining the temperature and/or chemical composition. 
     In order to avoid falsifications of the measured values, the emitting electromagnetic waves are cleared from electromagnetic waves ( 36, 37, 39, 40 ) directed obliquely to the optical axis ( 38 ) of the optical system ( 20 ) and present beyond a limit radius ( 41 ) drawn from the optical axis ( 38 ) of the optical system ( 20 ), by refracting said electromagnetic waves ( 36, 37, 39, 40 ) away from the optical axis ( 38 ) of the optical system ( 20 ) in a wave dispersion means ( 42 ) of the optical system ( 20 ) and only electromagnetic waves directed approximately parallel to the optical axis ( 38 ) of the optical system ( 20 ) arrive at a detector ( 22 ) arranged to follow the optical system ( 20 ), and/or the optical system ( 20 ) is moved relative to the hollow space ( 26 ) while adjusting its optical axis ( 38 ), until the intensity of the emitting electromagnetic waves yields a maximum during evaluation of the same (FIG.  2 ).

This application is the national phase under 35 U.S.C. §371 of prior PCTInternational Application No., PCT/AT96/00255, which has anInternational filing date of Dec. 19, 1996, which designated the UnitedStates of America, the entire contents of which are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for determining electromagnetic wavesoriginating from the interior of a melt, in particular a metal melt,especially in the visible light range and the adjacent UV range andinfrared range, wherein a gas-filled hollow space is formed within themelt by blowing in gas and electromagnetic waves emitting from the meltare observed through the blown-in gas and evaluated by feeding theelectromagnetic waves via an optical system to a detector fordetermining the temperature and/or chemical composition, as well as anarrangement for carrying out the method.

2. Related Background Art

In the production of steel in a converter or any other metallurgicalreactor by refining pig iron or treating other melts in such ametallurgical vessel, it has always been endeavoured to have availableas continuously and quickly as possible the temperature values of themelt and/or an analysis of the melt during the active treatment processin order to be able to keep the treatment process as short as possibleand to get as near as possible to the target analysis sought. Rapidityis required, in particular, because the chemical reactions proceed athigh speeds, involving the danger of being no longer able to interferewith the refining process or treatment process in due time. Theextremely rough operating conditions prevailing in such plants do notmeet with these objects. In the production of steel in a metallurgicalreactor (converter, electric furnace, etc.), in the secondarymetallurgical treatment of steel melts or in respect of any othernon-ferrous metal melts (e.g., Cu, Ni, Al) it is, furthermore,advantageous to know the temperature and/or analysis of the melt aftereach treatment stage.

To solve these problems, attempts have, for instance, been made to gethints as to the correct point of time for terminating a refining processfrom the spectral analysis of the converter flame or from its absorptiveeffect relative to monochromatic light of a defined wave length.However, the strongly varying blowing conditions and the foaming slag onthe melt bath as well as the high content of dust contained in theoffgas do not allow for sufficiently precise conclusions on thetemperature of the bath and the analysis of the melt.

Furthermore, it had been proposed for temperature measuring (DE-B-14 08873) to insert into the refractory lining of the converter encapsulatedthermocouples, which project into the converter interior and in theoperating position of the converter come to lie below the meniscus ofthe melt to be refined. However, the durability of such thermocoupleswas insufficient; in addition, measuring results have been adverselyaffected by the necessarily strong cooling of the measuring device.

Furthermore, it is known to determine the temperature of a melt at apredetermined point of time by means of lances submerged in the melt.That method is disadvantageous if applied to the production of steel ina converter, because to that end the converter must be tilted and setright again, which involves a temperature loss of the steel bath of upto 40° C. In addition, that method is time-consuming, because at firstthe blowing lance must be extended prior to tilting the converter andthe converter must be set right again after having carried out ameasurement, and it is only afterwards that the blowing lance—ifnecessary—can be retracted and blowing can be continued. Furtherdrawbacks include that the measuring point within the melt may be chosenonly arbitrarily, thus being hardly reproducible. Also the depth ofimmersion of the probe cannot be exactly determined, thus being hardlyreproducible, either.

The determination of a chemical analysis of the melt is evensubstantially more complicated. To this end, it is known to take samplesby means of lances submerged in the melt. When producing steel in aconverter this involves disadvantages since the taking of such sampleslikewise requires much time—the converter likewise having to be tilted(except with perpendicular sublance measurements)—and the samples mustbe sent to the laboratory.

When producing steel in a converter it is known to carry out a quickcarbon analysis by measuring the arrest point of the temperature and theC content. Thereby, it is however only feasible to acquire the Cequivalent such that some of the accompanying elements present in themelt have to be taken into account when calculating the actual carboncontent.

Furthermore, it is known to carry out carbon and oxygen activityanalyses and to take samples and temperature measurements in a converterby means of sub lances. This is, however, disadvantageous inasmuch asthe sublance means themselves (and also the samples) are very expensive,prone to extremely high wear and applicable only with liquid slagstowards the end of a blowing process.

From EP-B-0 162 949 a method for observing the formation of slag in asteel blowing converter, using the light radiation emitted from the slagsurface within the converter space is known. There, the light isphotoelectrically converted into signals and processed, variations ofthe signals being taken as criteria of foamed slag formation. Thereceptors inserted in the side wall of the converter are located abovethe slag/melt bath and are not suitable for measuring the melt bathtemperature and the melt composition.

From U.S. Pat. No. 4,830,601 a method and an arrangement for thespectral-analytical evaluation of the light emitted from the centralportion of a burner flame is known. There, the supply of fuel andcombustion air is surveyed by way of the light spectrum. Emitted lightis transmitted to an electronic evaluation device via fiber-opticconductors, the supply of combustion air and fuel being controlled as afunction of the gas analysis made.

A similar arrangement for temperature measurement in a process forproducing reducing gas in a high-temperature reactor at an elevatedoperating pressure is to be taken from DE-A-40 25 909.

From EP-A-0 214 483 it is known to verify the chemical composition ofiron by blowing oxygen or an oxygen-containing gas from top onto thesurface of molten iron, wherein beams originating from the melt surfaceare detected in a spectrometer with a view to determining the chemicalcomposition of the iron.

From U.S. Pat. No. 4,619,533 and EP-A-0 362 577 methods of the initiallydefined kind are known, wherein in the first case radiation originatingfrom the metal melt is conducted to a detector via a fiber-opticwaveguide. According to EP-A-0 362 577 laser light is focussed on themetal surface thus generating plasma. The plasma light emitted from themetal surface via a lens system and a fiber-optic waveguide is fed to aspectrometer for elementary analysis. The lens system comprisesadjustable lenses. The lenses are adjusted in a manner that the ratio ofthe intensities of two iron lines, namely the intensity of an atomicline arid the intensity of a ionic line, is minimal.

In a method of the initially defined kind, i.e., when detectingelectromagnetic waves originating from the interior of a melt, theblowing in of gas for the formation of a gas-filled hollow spaceadvantageously is effected through a wall opening of a metallurgicalvessel receiving the metal melt, said opening having to be located belowthe standard meniscus. In the region of transition of said opening ofthe metallurgical vessel towards the melt, i.e., in the marginal regionof said opening, reflections of the electromagnetic waves emitting fromthe melt are caused even with a very small opening, leading tofalsifications of the measured values. If a mushroom-shaped incrustationis formed of solidified melt as a result of the blown-in gas, theincrustation having the shape of a bead surrounding the marginal regionof the opening about the total periphery and oriented in the directiontowards the melt constitutes a disturbing factor despite its protectivefunction for the opening, constantly varying in size and position,whereby radiation originating from the surface of the incrustation orfrom the region of transition of the incrustation to the melt willfalsify the measuring result. It has been shown that a precisemeasurement can be carried out only if radiation originating exclusivelyfrom the melt surface is received and transmitted to the detector.Reflections from the marginal region of the opening or from theincrustation are strongly disturbing, i.e., bring about falsificationsof the measured values, without this being recognizable by any otherindications.

SUMMARY OF THE INVENTION

The invention aims at avoiding the above drawbacks and difficulties andhas as its object to provide a method of the initially defined kind, aswell as an arrangement for carrying out the method, by which thedetermination of desired measured values of a melt (such as, e.g.,steel, stainless steel, ferroalloys and melts of nonferrous metals) isfeasible in a simple manner practically without time delay and, inparticular, continuously as well as even with viscous to dry slags.Falsifications of the measured values caused by the measuring processitself and by the rough conditions of steelworks operation are to bereliably prevented, falsifications of the measured values having to beexcluded even with the hollow space provided within the melt being keptvery small.

In accordance with the invention this object is achieved in thatelectromagnetic waves directed obliquely to the optical axis of theoptical system and originating from the marginal region of the hollowspace are excluded from detection by clearing through opticalmanipulation the emitting electromagnetic waves from electromagneticwaves directed obliquely to the optical axis of the optical system andpresent beyond a limit radius drawn from the optical axis of the opticalsystem, by refracting said electromagnetic waves away from the opticalaxis of the optical system in a wave dispersion means of the opticalsystem, such as a dispersing and focussing lens system, and onlyelectromagnetic waves directed approximately parallel to the opticalaxis of the optical system arrive at a detector arranged to follow theoptical system, and/or in that the optical system is moved relative tothe hollow space while adjusting its optical axis, until the intensityof the emitting electromagnetic waves yields a maximum during,evaluation of the same.

According to a preferred embodiment, the wave dispersion means isfollowed by a wave bundling means, such as a focussing lens or afocussing lens system, and the electromagnetic waves directedapproximately parallel to the optical axis of the optical system arefocussed by the wave bundling means and fed to the detector directly orvia a fiber-optic waveguide, yet the oblique waves and those presentbeyond a limit radius are not covered by such focussing.

A further preferred embodiment is characterized in that both the wavedispersion means and the consecutively arranged wave bundling means aremoved relative to the hollow space while adjusting their optical axis,until the intensity of the emitting electromagnetic waves yields amaximum in the evaluation of the same. Thereby it is feasible to stillobtain optimum measuring results even with a particularly intensivecrust formation and/or strongly unilateral crust formation, i.e., withmelts being particularly prone to crust formation or with hollow spaceswithin the melt having small diameters.

To carry out a melt analysis, energy is suitably supplied to the meltthrough the gas-filled hollow space and a portion of the melt isevaporated by the energy supplied, the blown-in gas advantageouslyentering into a chemical reaction with the melt thus causing a portionof the melt to evaporate.

To protect the measuring procedure, the gas blown in to form thegas-filled hollow space, on the site of entering the melt, suitably issurrounded by a gas jacket or several gas jackets containing ahydrocarbon-containing protective medium, preferably mixed with inertgas. This will cause the formation of an incrustation of solidified meltensuring the supply of gas and also allowing for substantially gentletreatement of the arrangement required for carrying out a measurement aswell as a long service life of the same.

Simplification and acceleration of the method is provided if thedetermination of the temperature or chemical analysis of the melt iscombined with precalculited or measured parameters, such as a carboncomputation of the offgas analysis or a rough calculation of theanalysis of the melt at the time of measuring, and, furthermore, if onlythe contents of individual elements of the melt, such as, e.g., the Mn,Cr, C contents with iron melts, etc. are determined, the contents of theother elements or compounds contained in the melt and also in the slagmelt being calculated therefrom.

The accuracy of the method according to the invention may be enhanced inthat during measurement a temperature as close as possible to the actualtemperature of the melt is adjusted within the hollow space and/orimmediately in front of it by introducing a gas mixture.

Preferably the chemical analysis of the melt is concertedly changed, andthe melt or melt and slag are mixed thoroughly, by aid of a gas orseveral different gases introduced into the melt.

According to a preferred embodiment, the gas-filled hollow space isformed on the upper surface of the melt, for instance, by a gas feedduct including an optic device, a fiber-optic waveguide, a detector,etc. immersing into the melt.

An arrangement for carrying out the method, comprising

a vessel receiving a melt,

a gas supply duct leading to an opening of the vessel and including agas outlet opening oriented towards said opening and hence towards themelt,

an optical system for observing the gas outlet opening,

a detector for registering electromagnetic waves emitting from the melt,and

optionally a waveguide conducting the electromagnetic waves to thedetector, is characterized by

an optical wave dispersion means, such as a dispersing-focussing lenssystem and/or by

the optical system being arranged so as to be movable, preferablypivotable, relative to the metallurgical vessel.

A preferred embodiment is characterized by

a wave bundling means arranged to follow the wave dispersion means, suchas a focussing lens or a consecutively arranged focussing lens system,and

a detector located in the focussing zone of the wave bundling means or afiber-optic waveguide arranged there and leading to a detector.

Advantageously, a protective tube is provided for the optical system,comprising a gas flushing means, in particular a gas flushing meanscleaning the lens system on the front face. This is required, inparticular, if solids, such as, e.g., slag formers, dusts, in particularcoal dust, etc. are blown into the melt through the gas supply ductbetween the measuring periods.

Another preferred embodiment is characterized in that the wavedispersion means is pivotable relative to the gas outlet openingoriented towards the melt, the point of intersection of the optical axisof the wave dispersion means with the cross sectional area of the gasoutlet opening being adjustable within the cross sectional area thereof.

Suitably, both the wave dispersion means and the wave bundling means aremounted so as to be pivotable, the pivotable mounting advantageouslybeing realized by a cardanic mounting.

In the focussing region of the wave bundling means there is providedeither an inlet of a fiberoptic waveguide or the detector.

A suitable embodiment is characterized in that the end of the gas supplyduct is configured as a double- or multi-tube nozzle whose jacketannular space(s) is (are) Connectable to a duct feeding a hydrocarbongas. As a result, a crust of solidified melt is formed, which surroundsthe gas inlet opening in a manner that the multi-tube nozzle will bearranged in a well protected manner at the vessel, i.e., in thebrickwork of the vessel.

Preferably, the end of the gas supply duct is formed by a multi-channelnozzle whose nozzle openings are connectable to one or several supplyducts for hydrocarbon, carbon monoxide, carbon dioxide, inert gas,vapour, oil or water and/or mixtures thereof. As a result, thedurability of the jacket nozzle and the accuracy of the measurement maybe optimized while carrying out the measuring procedure and in generalby adjusting the amount and/or composition of the gases or liquidsintroduced through the annular gaps.

According to a preferred embodiment device oriented towards the gasoutlet opening of the gas supply duct is provide, as known per se fromEP-A-0 362 577, a focussing means suitably being associated with thelaser beam device.

Preferably, a gas supply duct comprising a wave dispersion means andimmersing into the melt is provided.

A method of operating an arrangement according to the invention ischaracterized in that, for protecting that part of the arrangement whichreaches into the vessel, the supply of the protective medium iscontrolled by continuously or step-wisely increasing the supply ofhydrocarbon-containing protective medium with the attack of the meltincreasing, i.e., with the temperature increasing of the melt beingoverheated.

BRIEF DESCRIPTION OF DRAWINGS

In the following the invention will be explained in more detail by wayof several exemplary embodiments schematically illustrated in thedrawing, wherein

FIG. 1 is a (partially sectioned) schematic overall view of thearrangement according to the invention and

FIGS. 2 and 3 each show a detail of FIG. 1 on an enlarged scale indifferent configurations

FIG. 4 depicts a special embodiment in an illustration analogous to FIG.3.

FIGS. 5 and 6 each present sections transverse to the plane of FIG. 2according to further embodiments.

FIGS. 7 and 8 schematically illustrate the beam paths according to theinvention.

FIG. 9 depicts a preferred embodiment in an illustration analogous toFIG. 3.

FIG. 10 represents a cross section through a gas supply tube in anillustration analogous to FIG. 4.

FIG. 11 relates to a further embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A metallurgical vessel 1, for instance, a refractorily lined converter(a vacuum vessel or an electric furnace or any other reactor, etc. mightbe provided as well) adapted to receive a steel melt 3 covered by a slaglayer 2, at a height located below the meniscus 4 of the steel melt 3with the converter 1 being normally filled, has an opening 5 in a sidewall 6, in which opening a gas supply duct 7 is inserted, which opensinto the interior 10 of the converter 1 on the inner side 9 of the sidewall 6 of the same by a gas outlet opening 8. Different gases, e.g.,oxygen, nitrogen, air, natural gas or mixtures thereof, as well asoptionally also solids, e.g., dusty carbon and/or slag formers and/ordusts, may be introduced through the gas supply duct 7, the gasesmentioned optionally acting as carrier gases for the solids. The gasesare stored in tanks 11 and are withdrawn via ducts 12 upon demand. Thesolids are stored in one or sevel conveying vessels 13 or are withdrawnfrom existing systems and supplied to the converter 1 by aid of aconveying gas, such as air according to FIG. 1. The composition of thegases and the choice and quantitative adjustment of the gases may beeffected by aid of a schematically illustrated valve stand 14.

According to the embodiment illustrated in FIG. 2, the end of the gassupply duct 7 is designed as a jacket nozzle 15, wherein a hydrocarbongas, optionally mixed with nitrogen, is introduced into the converter 1through an annular gap 17 surrounding a central tube 16 of the jacketnozzle, thereby inducing the formation of an annular incrustation 18protecting the mouth of the jacket nozzle 15 as a result of crackreactions. The end of the gas supply duct 7 also may be designed as asimple tube (without protective gas jacket) if durability is no point.

A branch tube 16′ arranged in the direction of the axis of the jacketnozzle 15 and in alignment therewith, which is equipped with a screen 19that may be provided with several adjacently arranged passage openingsfor the electromagnetic waves, opens into the central tube 16. Behindthe screen 19, there are provided an optical system 20 acting as afocussing lens and behind the optical system 20 the end of a fiber-opticwaveguide 21, for instance, a glass fiber conductor. The fiber-opticwaveguide 21 leads to a detector 22 responding to electromagnetic wavesand coupled with an amplifier and an electronic evaluation device 23.

The fiber-optic waveguide 21 and the optical system 20 advantageouslyare installed in a protective tube 24. Suitably, inert gas may beinjected into the branch duct 16′ via a duct 25, thus ensuring theoptical system 20 to be kept free of dust.

The arrangement functions in the following manner:

To carry out a temperature measurement, just gas—no solids—, preferablyinert gas, is blown into the converter 1 through the gas supply duct 7.In doing so, the gas pressure causes the formation of a hollow space 26filled by that gas, which follows immediately upon the annularly formedincrustation 18, thus being delimited by the same and by the meltsurface 27. The free passage opening for the gas safeguarded by theincrustation 18 is expected to have a minimum dimension of approximately0.2 to 1.0 cm².

From the melt surface 27 of the melt 3 delimiting the gas-filled hollowspace 26 electromagnetic waves are emitted, in particular, in thevisible light range and in the UV range. These electromagnetic waves,via the opened screen or flap 19 and the optical system 20, get to thefiber-optic waveguide 21 and, via the latter, reach the detector 22. Anelectronic evaluation device 23 enables the determination of thetemperature that is equivalent to the electromagnetic waves emitted in anatural way.

According to the embodiment represented in FIG. 3, the protective tube24 together with the fiber-optic waveguide 21 directly projects into thegas supply duct 7 n the region of its end designed as a jacket nozzle15. The protective tube 24 may be flushed with nitrogen, which, however,is not illustrated in detail.

According to FIG. 4, which depicts a section transverse to thelongitudinal extension of a gas supply duct, the gas supply duct 7 inits end region is configured as a multi-channel nozzle. In the center ofthe multi-channel nozzle, the protective tube 24 and the optical system20 including the fiber-optic waveguide 21 are provided. The protectivetube 24 is peripherally surrounded by two annular gap volumes 25, 26provided at a radial distance from each other, through which, forinstance, hydrocarbon gases may be injected into the converter 1.

The further annular gap volume 28 provided between the two annular gapvolumes 28″ and 28″′ is subdivided into several channels 28′ by means ofradial webs, said channels each extending over a partial peripheralregion, viewed in cross section. Through these channels 28′ other gases,such as, for instance, oxygen, inert gas or mixtures thereof, may beintroduced into the converter.

FIG. 5 depicts a measuring arrangement according to the invention,comprising a laser beam device 29, which may be used for carrying out amelt analysis. In this case, the protective tube 24 including thefiber-optic waveguide 21 is installed slightly eccentrical of the gassupply duct 7. The laser beam 30 generated by the laser beam device 29is oriented obliquely in the direction towards the gas outlet opening 8so as to pass through approximately the center of the gas outlet opening8, thus evaporating melt in the converter interior at the transition:gas bubble—liquid. The electromagnetic waves 31 emitting from theevaporated melt, which in FIG. 5 are indicated by wavy arrows, aredetected by the fiber-optic waveguide 21 and evaluated by means of theelectronic evaluation device 23. Preferably, the laser beam 30 isfocussed through a focussing lens, a focal spot being formed at theopening 5 between the gaseous and liquid surfaces of the melt 3.Suitably, the arrangement is devised so as to be movable in the beamdirection, thereby ensuring the optimum positioning of the focal spot.The gas supply duct 7 in its end region is configured as a jacketnozzle, hydrocarbon gases, inert gases or mixtures thereof beinginjected into the converter 1 through the annular space or annular gap17.

FIG. 6 represents a cross section through the end region of a gas supplyduct 7 according to a slightly modified form. The gas supply duct 7externally is comprised of a double jacket 32, hydrocarbon gases,nitrogen, etc. being injected through the annular space 33 formed by thedouble jacket. The internal volume of the gas supply duct 7 issubdivided several times by means of walls 35 extending radially and inthe longitudinal direction, i.e., into four spaced 34 of approximatelyequal size according to the exemplary embodiment illustrated. Throughone of the spaces 34 the laser beam 30 is directed into the interior ofthe converter 1 and through a second space 34 the protective tube 24comprising the lens system including the fiber-optic waveguide 21passes. Each of the spaces 34 may be fed with different gases, forinstance, with oxyen or inert gas or mixtures thereof.

From FIGS. 7 and 8, the beam paths preferred according to the inventionand illustrated schematically are apparent. Electromagnetic waves 36originating from the marginal region 35 of the hollow space 26 and ofthe opening 5, respectively, and, in particular, electromagnetic waves37 reflected from the incrustation 18 as well as electromagnetic waves39 propagating obliquely to the optical axis 38 of the optical system 20and electromagnetic waves 40 present beyond a limit radius 41 drawn fromthe optical axis 38 of the optical system 20 are excluded from detectionby said electromagnetic waves being refracted away from the optical axis38 of the optical system 20 by means of a wave dispersion means 42configured, for instance, as a dispersing and focussing lens system.

The wave dispersion means 42 is followed by a wave bundling means 43 bywhich the electromagnetic waves oriented approximately parallel to theoptical axis 38 of the optical system 20 are focussed. Theelectromagnetic waves 39, 40 oriented obliquely to the optical axis 38of the optical system 20 and present beyond a limit radius 41 drawn fromthe optical axis 38 of the optical system 20 are, however, not coveredby such focussing.

The difference between the variant illustrated in FIG. 7 and the variantillustrated in FIG. 8 is to be seen in that once the detector 22 islocated directely in the focussing zone 44 of the wave bundling means 43(FIG. 7) and once, according to FIG. 8, an inlet 45 of a fiber-opticwaveguide is located in the focussing zone, leading to a detectorcomprising an electronic evaluation device.

According to the embodiment illustrated in FIG. 9, the optical system20—which preferably comprises a wave dispersion means 42 and a wavebundling means 43—is pivotably mounted in the central tube 16,preferably in a manner that every point within the cross section of theopening 5 can be reached by the optical axis of the optical system 20.Such a movable mounting may be realized by means of severalpressure-medium cylinders 46 engaging at the optical system andindicated by arrows in FIG. 9 or by means of a cardanic mounting.Thereby, it is feasible to adjust the optical axis 38 of the opticalsystem 20 in a manner that it may be directed towards the melt 3 evenwith a unilateral growth of incrustation as illustrated in FIG. 9,falsifications of the measured values caused by the incrustation 18 thusbeing avoidable. In this case, the optical system 20 is pivoted untilthe intensity of the emitting electromagnetic waves yields a maximumduring evaluation of the same. This constitutes a criterion that theoptical axis of the optical system 20 is actually directed towards themelt 3 and not, for instance, towards the marginal region of theincrustation 3 or the marginal region of the opening 5. Displacement ofthe optical system 20 may be effected by aid of an electromechanic driveautomatically adjusting the optical system 20 in a manner that a maximumintensity will be developed. Furthermore, axial displaceability of theoptical system 20 may also be provided as indicated by the double arrow47, to which end electric motors or pressure-medium cylinders maylikewise be provided.

FIG. 10, in an illustration analogous to that of FIG. 4, shows a crosssection through a gas supply tube comprised of four concentricallyarranged cylindrical tubes 24, 48, 49, 50, intermediate spaces 51, 52,53 each being provided between the cylindrical tubes. The innermost tube24 serves as a gas supply tube for carrying out the measurement. Therethe optical system 20 and the fiber-optic waveguide 21 as well asoptionally the detector 22 are provided. The intermediate space 51radially following thereupon between the cylindrical tubes 24 and 48 isfilled with refractory material 54, wherein grooves 55 are yet providedon the external periphery of the refractory material, which are linedwith sheet metal coverings 56, if desired. Protective gas, e.g., CH₄,CH₄+N₂, etc., is directed to the end of the gas supply duct 7 throughthese grooves. The annular space 52 radially following thereupon, in thecircumferential direction is filled with refractory material 54 byapproximately one fourth, the remaining three fourths of the annularspace 52 being free and serving to feed oxygen or oxygen mixed withother gases. The radially outermost annular space 53, in turn, serves tosupply a protective gas.

According to the embodiment represented in FIG. 11, a gas supply duct 7in which the optical system 20 and the signal sensors (fiber-opticwaveguide 21 and/or detector 22) are installed, by means of adisplacement mechanism not illustrated in detail and al lowing formovements in the directions of the arrows 57, 58 indicated in FIG. 11,is moved from above into the melt 3 through the upper surface 59 of thesame, thus causing a gas-filled hollow space 26 to form within the melt3. Also in this case the end of the gas supply tube 7 may be configuredas a jacket nozzle so as to form a protective gas jacket.

Measurements may be carried out according to two different basicprinciples, namely once by aid of a pyrometer and once by aid of aspectrometer. Evaluation subsequently is effected via special electronicevaluation devices that differ with respect to the two systems.

The radiation emitting in the case of a pure temperature measurementdiffers from that intended for a melt analysis. During a melt analysisthe spectrum generated by a laser and emitted by a plasma is observed(UV range).

What is claimed is:
 1. An apparatus for determining characteristics of a melt comprising: a vessel for receiving a melt, a gas supply duct leading to an opening of the vessel and including a gas outlet opening oriented towards said opening and hence towards the melt, an optical system for observing the gas outlet opening, a detector for sensing electromagnetic waves emitting from the melt, and a waveguide conducting the electromagnetic waves along an optical axis of the optical system to the detector, the optical system including an assembly for optically manipulating the electromagnetic waves emitted from the melt to constrain said detector to exclude electromagnetic waves oblique to the optical axis and to detect electromagnetic waves substantially parallel to the optical axis.
 2. An apparatus according to claim 1, wherein said assembly includes an adjustment mechanism for moving the optical axis to a position where the detector senses only electromagnetic waves substantially parallel to the optical axis.
 3. An apparatus according to claim 2, further including a dispersion device for refracting electromagnetic waves obliquely directed from the optical axis away from the detector.
 4. An arrangement according to claim 3, further including a wave bundling apparatus arranged to follow the wave dispersion device, and a detector located in the focussing zone of the wave bundling apparatus.
 5. An apparatus according to claim 4, wherein the focussing zone of the wave bundling apparatus is optically coupled to an inlet of a fiber-optic waveguide.
 6. An apparatus according to claim 4, wherein the focussing zone of the wave bundling apparatus is optically coupled to the detector.
 7. An apparatus according to claim 3, wherein the wave dispersion device is pivotable relative to the gas outlet opening oriented towards the melt, the point of intersection of the optical axis of the wave dispersion device with the cross sectional area of the gas outlet opening being adjustable within the cross sectional area thereof.
 8. An apparatus according to claim 7, wherein both the wave dispersion device and the wave bundling apparatus are mounted so as to be pivotable.
 9. An apparatus according to claim 8, wherein the pivotable mounting is realized by a cardanic mounting.
 10. An apparatus according to claim 1, further including a protective tube provided for the optical system, comprising a gas flushing means for a front face of the optical system.
 11. An apparatus according to claim 1, wherein the end of the gas supply duct is configured as a multi-tube nozzle with annular spaces therebetween connectable to a duct feeding a hydrocarbon gas.
 12. An apparatus according to claim 1, wherein an end of the gas supply duct is formed by a multi-channel nozzle whose nozzle openings are connectable to one or several supply ducts for hydrocarbon gases.
 13. An apparatus according to claim 1, further including a laser beam device oriented towards the gas outlet opening of the gas supply duct.
 14. An apparatus according to claim 1, wherein said assembly comprises a dispersion device for refracting electromagnetic waves obliquely directed from the optical axis away from the detector.
 15. An arrangement according to claim 14, further including a wave bundling apparatus arranged to follow the wave dispersion device, and a detector located in the focussing zone of the wave bundling apparatus.
 16. An apparatus according to claim 15, wherein the focussing zone of the wave bundling apparatus is optically coupled to an inlet of a fiber-optic waveguide.
 17. An apparatus according to claim 15, wherein the focussing zone of the wave bundling apparatus is optically coupled to the detector.
 18. An apparatus according to claim 14, wherein the wave dispersion device is pivotable relative to the gas outlet opening oriented towards the melt, the point of intersection of the optical axis of the wave dispersion device with the cross sectional area of the gas outlet opening being adjustable within the cross sectional area thereof.
 19. An apparatus according to claim 18, wherein both the wave dispersion device and the wave bundling apparatus are mounted so as to be pivotable.
 20. An apparatus according to claim 19, wherein the pivotable mounting is realized by a cardanic mounting.
 21. A method for determining characteristics of a melt comprising the steps of: blowing gas into the melt to form a hollow space therein having marginal regions contiguous the melt; feeding electromagnetic waves emitted from the interior of the melt through the hollow space formed in the melt to an optical analyzer system having an optical axis extending from a central region of said space to a radiation detector outboard of the hollow space; optically manipulating electromagnetic waves emitted from the hollow space until a maximum intensity signal is sensed by the detector to thereby selectively detect electromagnetic waves traveling parallel to the optical axis, and selectively exclude electromagnetic waves emitted obliquely to the optical axis from said space; and determining characteristics of the melt by analyzing the electromagnetic waves sensed by the detector.
 22. The method of claim 21 including the further steps of: injecting a hydrocarbon-containing, protective, medium into the hollow space of the melt; and increasing the supply of said medium as the temperature of the melt increases.
 23. The method of claim 21 wherein the electromagnetic waves selectively excluded from being sensed by the detector are refracted away from the optical axis by a wave dispersion device.
 24. The method of claim 23 including the further steps of: providing a focusing lens at an output side of the wave dispersion device; and selectively focusing electromagnetic waves substantially parallel to the optical axis along the optical axis to the detector.
 25. The method of claim 24, wherein both the wave dispersion device and the focusing lens are disposed on the optical axis and are movable with the detector.
 26. The method according to claim 21, wherein energy is supplied to the melt through the hollow space and a portion of the melt is evaporated by the energy supplied, in particular, by blown-in gas entering into a chemical reaction with the melt, thus causing a portion of the melt to evaporate.
 27. The method according to claim 21, wherein the gas blown in to form the gas-filled hollow space on the site of entering the melt is surrounded by at least one gas jacket containing a hydrocarbon-containing, protective, medium mixed with inert gas.
 28. The method according to claim 21, wherein the melt characteristics determined include the temperature and chemical composition of the melt.
 29. The method according to claim 21, wherein during measurement a temperature as close as possible to the actual temperature of the melt is adjusted within the hollow space and immediately in front of it by introducing a gas mixture.
 30. The method according to claim 21, wherein the chemical composition of the melt is constantly changed, and the melt and slag therein are mixed thoroughly, by aid of at least one gas introduced into the melt.
 31. The method according to claim 21, wherein the hollow space is formed on an upper surface of the melt. 